The present technique relates generally to pneumatically operated devices. More specifically, a technique is provided to enable a pneumatically operated sprayer to relieve pressure from within the sprayer, while preventing cleaning liquids from entering the sprayer.
Automatic sprayers are used in manufacturing to apply a layer of coating to a work piece. For example, a manufacturer of toilets may use an automatic sprayer to apply a porcelain coating to the toilet bowl. Typically, automatic sprayers are pneumatically operated devices. Pressurized air is supplied to the automatic sprayer, which causes the sprayer to begin spraying. The pressurized air is removed to stop the automatic sprayer from spraying. A typical automatic sprayer has a spray control valve that is coupled to a diaphragm. Pressurized air is applied to one side of the diaphragm to drive the diaphragm in a first direction to unseat the spray control valve, enabling spray material to flow from the sprayer. A spring is provided to shut the flow control valve when the pressurized air is removed. During operation, pressurized air may leak around the diaphragm and cause the pressure across the diaphragm to equalize. When that occurs, the spring will shut the valve and cause the sprayer to inadvertently stop spraying. Consequently, sprayers have been provided with vents to prevent any air that leaks across the diaphragm from building up sufficient pressure within the sprayer to equalize the pressure across the diaphragm.
In addition, the material being sprayed occasionally is deflected back onto the sprayer. In the example of a toilet bowl provided above, the limited space inside the toilet bowl forces the automatic sprayer to be positioned close to the surface of the toilet bowl during spraying. This increases the likelihood that some of the spray material will be deflected back onto the sprayer. Similarly, in multi-sprayer applications, one sprayer may be aligned to spray material on at least a portion of another sprayer. As a result, automatic sprayers may be routinely washed or hosed down to prevent the buildup of spray material on important parts of the sprayer. If the spray material is not removed, it may interfere with the operation of the sprayer and/or produce defects in the coating applied by the sprayer.
However, problems have been experienced with washing down automatic sprayers. The vents that prevent air leaks from inadvertently stopping operation of the sprayer also enable water or other cleaning solutions to enter the sprayer during cleaning. These cleaning liquids may cause the internal components of the sprayer to rust or otherwise lead to failure of the sprayer. Accordingly, a technique is needed to address the foregoing problems.